Evacuees waded through flowing muddy waters, a few prized possessions perched on their heads. Others scrambled to climb atop roofs to avoid drowning.

"In Chokwe, one of the hardest hit districts -- the normally vibrant streets now lie under water --all business brought to a standstill and social services shut down," the United Nations said.

Preliminary information indicates at least $15 million will be needed for the relief operation. The United Nations warned that the amount is expected to go up as assessment teams release more information.